Electron-impact ionization cross sections out of the ground and6P2excited states of cesium

Abstract

An atom trapping technique for determining absolute, total ionization cross sections (TICS) out of an excited atom is presented. The unique feature of our method is in utilizing Doppler cooling of neutral atoms to determine ionization cross sections. This fluorescence-monitoring experiment, which is a variant of the ``trap loss'' technique, has enabled us to obtain the experimental electron impact ionization cross sections out of the Cs $6\phantom{\rule{0.2em}{0ex}}^{2}{P}_{3∕2}$ state between $7\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and $400\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. CCC, RMPS, and Born theoretical results are also presented for both the ground and excited states of cesium and rubidium. In the low energy region $(<11\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ where best agreement between these excited state measurements and theory might be expected, a discrepancy of approximately a factor of five is observed. Above this energy there are significant contributions to the TICS from both autoionization and multiple ionization.